More than 6 inches of rain could fall in parts of New Jersey hardest hit by the thunderstorms Thursday afternoon into Friday morning, the weather service said.

"Rainfall rates may exceed 2 inches per hour," the National Weather Service added. In Pike and Wayne counties, the watch starts at noon. Districts 4 and 5 of the Pennsylvania Department of Transportation, which each cover part of the Poconos, issued reminders on July 30 for drivers not to drive through flooding on roads.

Storms and flood threats are headed for the New York City area, prompting a string of First Alert Weather Days through the end of the work week. Heavy rain that may cause flooding is expected both Thursday and Friday.